Adapt to changes in Gerrit API

AccountCache#getOrNull was renamed to maybeGet and returns an
Optional<AccountState> instead of a nullable AccountState now.

Change-Id: I65378edd142ed84f35d7c0a666766d977dccac78
Signed-off-by: Edwin Kempin <ekempin@google.com>

src/main/java/com/googlesource/gerrit/plugins/singleusergroup/SingleUserGroup.java

diff --git a/src/main/java/com/googlesource/gerrit/plugins/singleusergroup/SingleUserGroup.java b/src/main/java/com/googlesource/gerrit/plugins/singleusergroup/SingleUserGroup.java
index 327849d..08b11a1 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/singleusergroup/SingleUserGroup.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/singleusergroup/SingleUserGroup.java
@@ -106,7 +106,7 @@
     String ident = username(uuid);
     Optional<AccountState> state;
     if (ident.matches(ACCOUNT_ID_PATTERN)) {
-      state = Optional.ofNullable(accountCache.getOrNull(new Account.Id(Integer.parseInt(ident))));
+      state = accountCache.maybeGet(new Account.Id(Integer.parseInt(ident)));
     } else if (ident.matches(Account.USER_NAME_PATTERN)) {
       state = accountCache.getByUsername(ident);
     } else {